Mass Spectrometry (MS) is a 100-year old technology that relies on the ionization and fragmentation of molecules, the dispersion of the fragment ions by their masses, and the proper detection of the ion fragments on the appropriate detectors. There are many ways to achieve each of these three key MS processes, and this gives rise to different types of MS instrumentation systems having distinct characteristics.
Four major types of ionization techniques are commonly used to both break apart a larger molecule into many smaller molecules and at the same time ionize them so that they can be properly charged before mass dispersion. These ionization schemes include Electrospray Ionization (ESI), Electron Impact Ionization (EI) through the impact of high-energy electrons, Chemical Ionization (CI) through the use of other reactive compounds, and Matrix-Assisted Laser Desorption and Ionization (MALDI). Both ESI and MALDI also serve as means for sample introduction.
In particular, the electrospray ionization technique is a technique for spraying a sample molecule (which is brought into an ionic state by acid, or the like, in the solution) by applying a high voltage; forming liquid droplets (mist) on the order of microns, in which many solvent molecules are combined with protonated or ionized molecules; and spraying a liquid to dry and remove the solvent, followed by introducing the ions to an appropriate mass analyzer.
Each ion will have a corresponding mass-to-charge (m/z) ratio, which will become the basis to mass dispersion. Based on the physical principles used, there are many different ways to achieve mass dispersion, resulting in mass spectral data. A few of the commonly seen configurations include magnetic sectors, quadrapoles, Time-Of-Flight (TOF), and Fourier Transform Ion-Cyclotron Resonance (FT ICR).
However, there is a need in the art for novel ionization sources.